Display panel or portion thereof with a graphical user interface



FIG. 1 is a front view of a display panel or portion thereof with agraphical user interface showing a first embodiment of our design; and,

FIG. 2 is a front view of a display panel or portion thereof with agraphical user interface showing a second embodiment thereof.

The outmost broken line rectangle illustrates a display panel or portionthereof that forms no part of the design. The reaming broken lines,including all text, illustrate portions of the graphical user interfaceor mixed reality environment and form no part of the claimed design.

CLAIM The ornamental design for a display panel or portion thereof witha graphical user interface, as shown and described.